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Despite a focus on diet, calorie intake may not be the
major factor causing death by heart disease, according
to a 17-year study of almost 10,000 Americans. The study
appears in the American Journal of Preventive Medicine.
Losing
excess weight — or not becoming overweight to begin
with — and exercising may do more to ward off death
from heart disease, say Jing Fang, colleagues from the
Albert Einstein College of Medicine in New York.
"The
fact is that those who both exercised more and ate more
nevertheless had low cardiovascular mortality,"
says Fang. Expending energy through physical activity
may be the key to cutting the risks of heart disease
and living a longer, more healthful life, she says.
The
researchers studied data from 9,790 participants in
the First National Health and Nutrition Examination
Survey, a national study from 1971 to 1975 that was
funded by the U.S. government. Fang's group compared
reports of physical activity, body mass index and dietary
caloric intake to deaths from heart disease through
1992.
They
grouped participants by their initial reports of caloric
intake (low, middle, high), recreation exercise (least,
moderate, most) and body mass index (normal, overweight,
obese). Body mass index is a measure of weight in relation
to height.
Overweight
and obese participants, those who consumed fewer calories,
and those who exercised less were also likely to be
older, black, have a lower family income, less likely
to have graduated high school, and more likely to have
higher blood pressure and cholesterol levels than those
who ate and exercised more.
During
17 years of follow-up, 1,531 participants died of heart
disease. After adjusting for BMI and physical activity,
caloric intake was unrelated to heart disease. Those
who exercised more and ate more were both leaner and
had less than half the cardiovascular disease mortality
than did those who exercised less, ate less and were
overweight.
"Subjects
with the lowest caloric intake, least physical activity,
and who were overweight or obese had significantly higher
cardiovascular mortality rates than those with high
caloric intake, most physical activity, and normal weight,"
Fang says. The difference in mortality rates was 55
percent.
Those
who eat less won't necessarily be thinner, she says,
and eating more does not have to translate into obesity.
People who were overweight and exercised less at the
start faced increased cardiovascular mortality, even
if they ate less.
"This
suggests that heart disease outcome was not determined
by a single factor, but rather by a compound of behavioral,
socioeconomic, genetic and clinical characteristics,"
she says.
A
focus on increased energy expenditure rather than reduced
caloric intake may be the most practical outcome of
this study, she says, and may offer the most productive
behavioral strategy by which to extend healthy life.
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